And annie e



UNITED STATES PATENT OFFICE.

H, JEROME BURR, OE BLOOMFIELD, ASSIGNOR OF ONE-HALF TO WM. EDGAR SIMONDS, OF HARTFORD, CONNECTICUT, AND ANNIE E. BURR, ADMIN IS- TRATRIX OF SAID BURB, DECEASED, ASSIGNOR OF THE REMAINING ONE-HALF To SAID SIMONDS.

' HARDENING IRON.

SPECIFICATION forming part of Letters Patent No. 280,716, dated July 3, 1883.

Application filed April 30, 1881. (No specimens.)

To all whom it may concern.-

Be it known that I, H. JEROME BURR, of Bloomfield, in the county of Hartford and State of Connecticut, have invented a certain new and useful Improvement pertaining to Hardening Malleable Cast-Iron, of which the following is a description.

It is well known that malleable cast-iron may be hardened upon the surface by the pro- If) cess known as case-hardening.

The present improvement relates to hard ening malleable cast-iron, not merely superficially, as by case-hardening, but bodywise, and so that the hardening extends into the body of the malleable iron, and, indeed, en-

tirely through the article, provided that the article be not too thick, and that it be malleable throughout before its submission to the process herein described. I am not able to state to what depth this hardening may be made to penetrate a body of malleable castiron; but experiments indicate that such hardening penetrates to the entire depth to which the article is first made malleable, taking for that purpose malleable cast-iron as now commonly made and found in the markets. By malleable cast-iron I mean cast-iron made malleable by the known and common process of cementation or annealing.

The invention consists in the process herein described, and in the product which is the inevitable result of that process, which product cannot, as I believe, be reached or attained by any other process than that herein described.

This process consists in heating the article of malleable iron in contact with a mixture of comminuted iron, prussiate of potash, and borax, and then suddenly cooling the heated article in cold water or other suitable medium. The product consists inmalleable cast-iron hardened by heated contact with prussiate of potash, comminuted iron, and borax, and sub sequent sudden cooling, substantially as herein 4 5 described. The mixture referred to should be in the form of a powder, and it may be made to adhere to the article on which the process is being practiced by wetting the article and touching the wetted part to the powder. The hardness attained is affected by the degree of heat used; red heat gives less hardness than a cherry heat, and it is not advisable to use higher than a cherry heat. Alum-water or salt-water for the hardening-bath also increases the hardness. .The mixture referred to is composed of comminuted wrought-iron, prussiate of potash, and borax. The preferable degree of fineness of the comminuted iron is that of filings made with a fourteen-inch file. In mixing the ingredients the prussiate of potash may be reduced to powder, the borax inelted, and when cold reduced to powder, and the component parts be intimately mingled by grinding them together. This mixture is useful to a degree for the purpose herein indicated in any proportion which gives a sub stantial part of each ingredient; but the pro portions which give special efficacy are (by weight) two parts of prussiate of potash to one part of comminuted iron and one part of borax.

This improvement is specially valuable in making various articles of iron. They can be first east to substantially the shape of the desired article, then made malleable, and the malleable portion, or any desired part thereof, be then hardened in the manner described.

I am not able to explain with certainty the manner or mode in which the said mixture or its ingredients take effect in the practice of 80 this process; but experiments indicate that the prussiate of potash and-the comminuted iron are theeffective elements in effecting the hard ening, and the borax serves the purpose of a flux. 8 5

Prussiate of potash has beenv heretofore used in case-hardening, and borax has been heretofore used as a fiux; but considerable research fails to show that comminutediron has ever been used at all for hardening either iron 0 proportions herein described, is reserved as the subject-matter of another application for Letters Patent.

I claim as my i1np1'ove1nent l. The art or process of hardening inalieable east iron bedywise, consisting in heating it in contact with prussiaiie of potash, coin ininuted iron,and borax, and then suddenly cooling it, substantially as herein described.

2. Malleable east-iron hardened bodywise 10 by heated contact with prnssiate of potash, eoinnrinuted iron, and borax, and subsequent sudden cooling, substantially as herein described.

H. JEROME BURR.

\Vi tnesses:

W M. E. SIMONDS, (inns. L. ZURDETT. 

